Ventless tire mold

ABSTRACT

A tire molding apparatus and technique is provided for the ventless molding of tires. According to the invention, a series of pitches is formed in an appropriate REN board, plaster, or like material with the implementation of a CNC machine. An aluminum pour casting is made from the model in which the various pitches are separated by voids which allow for the entry of a cutting tool such that each individual pitch or tire tread segment can be cut from the aluminum casting. Sipe locations are then cut into the model. Master rubbers or foundry tooling is then created and the castings poured. The individual pitches are then matingly interengaged in a puzzle-like fashion along the interior of a tire mold to define the tread portion of the mold. Venting of the mold is achieved at the pitch line formed at the intersection of each of the pitches.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/703,243 filed Nov. 1, 2000.

TECHNICAL FIELD

The invention herein resides in the art of tire molding apparatus andtechniques. More particularly, the invention relates to a ventless tiremold. More specifically, the invention presents a ventless tire moldwhich is made of a plurality of interconnecting pitches, with theinterface of the pitches serving as vent lines for the mold cavity.

BACKGROUND ART

It is well known that the manufacture of pneumatic tires typicallyrequires the implementation of a mold and associated tire presses toform the tire tread in the green rubber and to hold the tireconfiguration while the green tire cures. In the past, the preparationof tire molds has generally been extremely labor intensive and involvedhighly skilled manual labor, both resulting in significant cost in thedevelopment of a tire mold.

In the past, it has generally been known to employ a hand carver acomputerized numeric controller (CNC) machine to make a master model ofan appropriate material such as REN board, plaster, or the like. Fromthe master model, foundry tooling is made and ultimately from thefoundry tooling cores are developed. As is understood by those skilledin the art, a core is a sequence of pitches or tire tread elements. Anappropriate number of cores with the requisite pitch sequences for thedesired tread pattern were necessarily generated. These cores were thenmated in the proper diameter and pitch sequence to define the requisitemold. This assembly was then cured and employed to make castings, fromwhich the molds themselves could ultimately be made.

In the prior art process of casting tire cores, a number of shortcomingswere present. Generally, undercuts were impossible to achieve except bytedious handwork. However, such undercuts are common in tire designswhere sipes must be employed. Additionally, prior art molds necessarilyrequired a large number of pinhole vents to allow air to escape from themold as the tire was expanded into the mold during the curing operation.These pinhole vents required continuous cleaning and removal of curedrubber to prevent such blockage from impairing the efficiency of themold.

As one can readily appreciate, these prior art mold designs areextremely time consuming and costly to manufacture, implement andmaintain. Accordingly, there is a need in the art for a tire moldingapparatus and technique which overcomes these shortcomings of the priorart.

SUMMARY OF INVENTION

In light of the foregoing, it is a first aspect of the invention toprovide a tire molding apparatus and technique which is of a ventlessnature.

Another aspect of the invention is the provision of a tire moldingapparatus and technique in which segments of the tire mold are assembledsingle pitches, rather than cores.

Still a further aspect of the invention is the provision of tire moldingapparatus and technique in which the venting of the mold is at the pitchline formed at the intersection of mating pitches, rather than throughthe addition of pinhole vents.

Still a further aspect of the invention is the provision of a tiremolding apparatus and technique in which a model is made of a REN board,plaster or the like, sipes are set in the model itself then traditionalmaster rubbers can be made.

A further aspect of the invention is the presentation of a tire moldingapparatus and technique in which a mold may be developed by casting ofsingle pitches, rather than entire cores.

Still a further aspect of the invention is the provision of a tiremolding apparatus and technique which is readily conducive toimplementation with state of the art materials and processes.

The foregoing and other aspects of the invention which will becomeapparent herein are achieved by a ventless tire mold, comprising: aplurality of mold segments nestingly interconnecting with each other atsegment interferences to form an annular mold, said segment interfacesdefining air passages from an interior of said annular mold.

Other aspects of the invention which will become apparent herein areattained by a method for making a ventless tire mold, comprising: (a)developing three dimensional models of tire tread portions; (b)installing sipes into the models; (c) generating foundry castings fromthe siped models; (d) preparing individual pitch profiles from saidfoundry castings; and (e) assembling a mold by nestingly interconnectinga plurality of said prepared individual pitch profiles.

DESCRIPTION OF THE DRAWINGS

For a complete understanding of the objects, techniques and structure ofthe invention reference should be made to the following detaileddescription and accompanying drawings wherein:

FIG. 1 is a perspective view of an aluminum casting of a plurality ofpitches made in accordance with the invention;

FIG. 2 illustrates a pair of pitches cut from a casting such as thatshown in FIG. 1;

FIG. 3 is a perspective view of half of a mold made by sequentiallyinter-fitted pitches.

FIG. 4 is a flow chart of the tire mold/model casting process accordingto the prior art;

FIG. 5 is a flow chart of the mold machining process of the prior art;

FIG. 6 is a flow chart of the tire mold/model casting process accordingto the invention; and

FIG. 7 is a flow chart of the mold machining process according to theinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

In accordance with the concept of the present invention, a tire moldwill be made of a plurality of interconnected pitches, each pitchconstituting a segment of a tire tread, and wherein the pitch linesdefined by the mating interfaces of the pitches serve as air passagevents for the tire mold cavity. In effect, the tire mold is made in apuzzle-like fashion with the pitches comprising the pieces of the puzzlethat inter-fit with each other to ultimately define the mold, and inwhich the interfaces between the puzzle pieces serve as mold vents.

In accordance with the invention, a model is made by carving a RENboard, plaster, or the like by use of a multi-axis CNC machine insomewhat standard fashion. The carving in the REN board, plaster, or thelike is a sequence of pitches having void spaces between them so that atool path is present to cut each of the individual pitches along thepitch line. Once the pitches are cut, undercut ribs for incorporatingsipes in the model may be easily achieved.

As shown in FIG. 1, an aluminum casting 10 can be made from the model ofREN board, plaster, or the like in somewhat standard fashion. Thealuminum casting 10 includes a plurality of pitches 12 separated byseparator blocks 14. The voids between the blocks 14 and above pitches12 allow for entry of an appropriate cutting tool to cut the pitchesalong the cut lines 16 defined by the intersection of the separatorblocks 14 and pitches 12. As a consequence, the individual pitches 18,as shown in FIG. 2, are developed. As illustrated, the vertical sides 20of the pitches 18 are contoured to mate with each other and are defmedby the cut lines 16 as presented in FIG. 1. The vertical sides 20 definethe pitch lines by which various pitches 18 nest with each other.

The nesting of the various pitches 18 to form the tread portion of atire mold is illustratively shown in FIG. 3. Here, it can be seen thatone half of a tire mold made in accordance with the invention isdesignated generally by the numeral 28. It will be appreciated by thoseskilled in the art that the tire mold 28 is typically of but not limitedto the clamshell type mold, comprising upper and lower clamshell halvesthat are brought into sealing engagement with each other with a greentire carcass therein. This same process in creating models and moldparts may also be used in segmented molds. The tire mold being of aclamshell or segmented type is held shut by an appropriate tire pressand the green tire is inflated by a bladder and urged against the innerwalls of the tire mold. In this instance, the tread portion of the tiremold 28 is defmed by a plurality of abuttingly interconnecting pitches18, each abutting at pitch lines 20 defined by the interface of thevertical sides of the pitches themselves. These interfaces provide airpassages for venting of the mold as the tire mold bladder is inflated tourge the green tire carcass into conforming engagement with the innersurface of the mold 28, and particularly the annular array of pitches18.

Those skilled in the art will readily appreciate the simplicity by whichthe puzzle mold of the instant invention may be configured. Rather thandevise a plurality of cores of appropriate diameter and pitch sequencefor interfitting to define a mold, individual pitches may be made from aCNC carved model of REN board, plaster, or like material and then by asubsequent pour casting technique. The aluminum cast pitches, defmed byvoids therebetween, may then be easily cut from the aluminum casting somade, with each of the pitches then being easily operated upon toprovide undercuts for sipes or the like in each individual pitchelement. The various pitches 12 are then also machined for close nestingengagement with each other and to a desired smooth release surface forformation of and engagement with the tire tread. Moreover, the multitudeof pinhole vents previously employed in the previous art have beeneliminated, greatly reducing the cost of not only manufacturing themold, but maintaining it.

An appreciation of the advantages of the instant invention over theprocess and techniques of the prior art can best be achieved by acomparison of the two through reference to FIGS. 4-7. As shown in FIG.4, the prior art process for manufacturing the tire mold model/castingis designated generally by the numeral 30. As shown, engineeringspecifications for the associated tire are received from the customer,such as a tire manufacturer as designated at 32. Template layout andprogram is then undertaken and checked until the template layout isdeemed satisfactory as at 34-38. The sweep template is then cut at 40and the model is swept and checked at 42-44. Only then, can a modellayout be made at 46. But that process includes repeated inspection andmodification until the model layout is deemed satisfactory at 48.

After the model layout is complete, model carving and inspection isundertaken at 50-52 until a suitable carving is obtained. The carving isfinished by point up at 54.

Those skilled in the art will also appreciate that the specificationreceived from the customer at 32 also includes the specificationregarding the sipes necessary for the model rubber tooling. Thosespecifications are passed to a sipe manufacturer at 56, who undertakessipe preparation and inspection until the sipes are complete at 58. Thesipes are then placed onto the carving at 60 and checked for accuracy at62.

The core boxes for the model tooling are determined at 64 followingmodel sweep check 44. The model rubber tooling is then prepared at 66from the siped carving and the model rubber tooling is pointed up at 68into a finished structure for casting of the master models at 70. Thecastings are checked at 72, round up and assembly undertaken at 74 andthe casting pointed up at 76. Finishing of master model is undertaken at78 where all of the final lines of the model are finished. Followingfinal inspection at 80, the foundry tooling is prepared at 84 and thefoundry castings made at 86.

With reference now to FIG. 5, it can be seen that the tread castingscompleted at 86 are received from the foundry at 92 and verified foraccuracy at 94. Rough cuts on the castings are made for outsidediameter, inside diameter, and parallel sides at 96. They are then roughdrilled at 98 and finished at 100. Following an in process inspectionfor verification of accuracy at 102 the vent layouts are prepared at104. Spot vents are prepared by center punch at 106 and vent holes aredrilled on location at 108. The vent backside is channeled at 110 andthe vent is chamfered and set at 112. Thereafter, the micro-vents areinstalled at 114 at the numerous vent locations just prepared. The ventsare inspected at 116 and reworked at 104-114 until the vents have allbeen approved.

Next in the process, the mold back or slide block is machined to acceptthe requisite tread ring at 118 and the tread ring is then assembledinto the mold back or slide block and final machining is undertaken at120. The mold is inspected at 122 and any necessary further machining isundertaken until the mold is deemed acceptable. The mold is thencompleted at 124 for tire manufacturing.

In contrast to the labor intensive methodology for prior tire molddevelopment, including the placement of a multitude of tire vents, isthe process of the instant invention as shown in flow chart form inFIGS. 6 and 7.

With reference now to FIG. 6, an appreciation of the manufacturingprocess for the ventless tire mold/model casting according to theinstant invention can be seen as designated by the numeral 130. Again,drawings or engineering specifications are received from the customer at132 and a verification of the information so received is made at 134.Three dimensional models are then developed at 136 and a multi-axis CNCmachine is employed to cut the models at 138. The model is assembled at140 and inspected at 142. The model assembly is pointed up at 144 andreadied for receipt of the requisite sipes. As will be appreciated bythose skilled in the art, information respecting the sipes was receivedin the way of specifications from the customer at 132, verified at 134,and delivered to a sipe manufacturer at 146. The sipes are inspectedupon receipt at 148 and then installed into the pointed up modelassembly at 150. The final model is inspected at 152 and any additionalmodifications made. The final lines are imparted at 154.

It will further be appreciated by those skilled in the art that once themodel is assembled at 140, the core boxes for foundry tooling can bedefmed at 156 such that the foundry tooling can be devised at 158 fromthe finished model. The foundry castings are then prepared at 160.

With reference now to FIG. 7, the process 170 shows receipt of the treadcastings from the foundry at 172 and verification of the same foraccuracy at 174. Rough cutting of the outside diameter, inside diameterand parallel surfaces is undertaken at 176, rough drilling at 178 andfinished cutting a 180. With verification for accuracy being undertakenat 182.

In stark contradistinction to the prior art, at 184 finished CNCmachining of individual pitch profile from tread ring casting isundertaken and the pitch profiles are removed from the tread castingring at 184. Each of the individual pitches is inspected at 186 andfurther machining undertaken until the requisite machining is complete.The mold back or slide block is then machined to receive and accept eachof the various tread pitch castings until completed at 188. Treadpitches are then assembled into the mold back or slide block at 190 withappropriate retention rings to retain each of the pitches therein.Finished machining of the mold as required for completion is alsoundertaken at 190. The mold is inspected at 192 and necessary furthermachining undertaken. The tire mold, comprised of a multitude ofinterconnected and interfaced pitches, is completed at 194.

Following the process of the instant invention, a mold comprising aplurality of interfaced pitches is achieved, with the venting of themold being accomplished at the pitch interfaces, thus obviating the needfor drilling, finishing, and placing of micro-vents throughout the molditself. Moreover, maintenance of the mold is simplified since periodiccleaning of the micro vents is obviated.

Thus it can be seen that the objects of the invention have beensatisfied by the structure presented above. While in accordance with thepatent statutes, only the best mode and preferred embodiment of theinvention has been presented and described in detail, the invention isnot limited thereto or thereby. Accordingly, for an appreciation of thetrue scope and breadth of the invention, reference should be made to thefollowing claims.

1. A ventless tire mold, comprising a plurality of mold segmentsnestingly interconnecting with each other at segment interfaces to forman annular mold, said segmented interfaces defining air passages from aninterior of said annular mold.
 2. The ventless tire mold according toclaim 1, wherein said segments comprise tire tread pitches.
 3. Theventless tire mold according to claim 2, wherein side surfaces of saidsegments are contoured for mating engagement of said segments.
 4. Theventless tire mold according to claim 2, wherein said annular mold isabsent vents within said segments themselves.